1. Field of the Invention
Dolphins possess a keen sonar capability that allows them to detect and discriminate targets in highly cluttered and noisy environments. Their biosonar abilities far exceed those of any man-made sonar to detect and discriminate targets in shallow waters typical of coastal and estuary environments. One outstanding example of the dolphin""s keen sonar capabilities is its ability to detect small fish and eels buried 30-45 cm beneath the sandy seabed in the sand banks of the Bahamas.
2. Description of Related Art
The related art is primarily the U.S. Navy""s xe2x80x9cMK-7 Marine Mammal Systemxe2x80x9d, which is a mine-hunting system to detect and classify mines buried in the ocean bottom. The MK-7 system relies on trained Atlantic bottlenose dolphins, Tursiops truncatus (xe2x80x9cdolphinxe2x80x9d). Man-made sonars developed to date typically cannot detect, discriminate, and classify shallow water mines buried in the ocean bottom. The dolphin""s scanning capabilities coupled with their apparently good auditory spatial memory provide considerably more information to a dolphin than can be achieved with traditional, man-made sonar systems. Auditory processing used by dolphins appears to be well suited for analyzing broadband, high frequency echoes.
There is no hull-mounted, swimmer-held, remotely operated vehicle-mounted, or autonomous underwater vehicle sonar that can discriminate and recognize targets, including without limitation mines and other armaments, that are buried in ocean sediment or veiled by turbid water.
The Biomimetic Sonar invention ensonifies submerged objects, digitizes acoustic images reflected from the ensonified objects, and classifies and stores the digitized images using electronic processing patterned on that believed to be used by Tursiops truncatus. The waveform, spectrum, and binaural processing of the dolphin echolocation system appear to be extremely important to the unique capabilities of the dolphin""s xe2x80x9cbiosonarxe2x80x9d.
A target that is ensonified with a broadband pulsed signal such as a dolphin-like (i.e., biomimetic) sonar signal will have unique time-frequency characteristics, or xe2x80x9chighlightsxe2x80x9d. The same target will generate different time-frequency characteristics when ensonified from different aspects. Such time-frequency characteristics are independent of the distance of the sonar from the target, assuming a sufficiently high signal-to-noise ratio. Therefore, multiple, related time-frequency characteristics of a specific target can be obtained by ensonifying that target from a plurality of different aspects. The signal in each receive channel in the Biomimetic Sonar will have slightly different time-frequency characteristics, providing more information and a better characterization of a target as to surface texture, structural relationships, thickness, etc. Sets of echo characteristics, called acoustic images, of known objects are collected as xe2x80x9cobject templatesxe2x80x9d in an object template library. The object templates are used to identify unknown ensonified objects by comparison of object templates with the acoustic images of an unknown object
The inventive step in the Biomimetic Sonar system lies in complex auditory processing, including the emulation of the displacement by acoustic energy of the basilar membrane in the dolphin cochlea, the generation of auditory neural network signals corresponding to echoes from objects in the ensonified space, the creation of two- and three-dimensional acoustic images based on those neural signals, classification of those acoustic images, comparison of those acoustic images with object templates stored in an object template library, and providing a probable identification of an ensonified object based on that comparison.
The Biomimetic Sonar can not only recognize and identify targets on the ocean floor, it can recognize and identify shallowly buried targets, targets in turbid water, and can discriminate mine-like targets from coral heads, oil drums, and other debris on the ocean bottom. In some cases, the Biomimetic Sonar can recognize and identify specific types of mines.